Everyone knows that it's only in UK that grades are predicted for UCAS, it's just a done thing. Everywhere else it's just not done. So if in your country grades are not predicted - just say so in the statement (or your teacher will say it in the reference), I do not understand why do you need to make them up. International applications are reviewed upon existing grades. Your admissions tutor will know if you just make them up, what's the point of lying?